In vivo Toxicity and Biodistribution Studies

For the in vivo biological toxicity, 200 μL of NRPNs solutions (20 mg/kg) was intravenously injected into 5 female BALB/c mice and 200 μL saline was intravenously injected into the other 5 female BALB/c mice as controls. These mice were sacrificed 14 days later. Then, the tissues of the brain, heart, liver, spleen, kidney and lung of each mouse were fixed with 4% formaldehyde solution and observed by H&E.

For assessment of the biodistribution and the magnetic targeting effect of the NRPNs, 200 μL of the NRPNs solutions (20 mg/kg) was intravenously injected into 10 tumor-bearing mice. Five mice were treated with magnetic targeting, the other 5 mice were treated without magnetic targeting. A magnet was placed next to the tumor region for 8 h for targeting. The maximum magnet strength was 6.0 Gs. At the 0, 1, 8, and 24 h time point, the fluorescence of each tumor was obtained with a Xenogen IVIS Spectrum in vivo imaging system. After 24 h, all of the tumors and major organs (brain, heart, liver, spleen, kidney, and lung) of the mice were ex vivo imaged by the fluorescence system.